White's TDI - Hi and Lo Conductivity

[OzzyGold]

Digger Bob and others!!
If I have gold nuggets in an area with say 5 to 10 percent silver would it be better to search in Hi Conductivity rather than Lo? Does the signal alter with nuggets that contain more silver?
regards

 

[steve herschbach]

Hi,

How the TDI responds to gold nuggets has more to do with size than purity, and even the shape can make a difference. So there is no hard and fast rule. In general, the vast majority of nuggets found, being on the small side, will give a high tone (low conductive). Large nuggets will give a low tone (high conductive).

So what is small and what is large? That is where the purity and shape kick in. Interestingly, even though silver is more conductive than gold, adding silver to gold actually lowers the conductivity. So a higher silver content will make the nugget more prone to a high tone, low conductive response. Solid, round nuggets will tend more towards reading low tone, high conductive, than gold with lots of quartz mixed in.

My recommendation is to dig all tones until a clear pattern develops in any given location. Having some knowledge of whether an area has ever produced multi-ounce nuggets is helpful. I hunt places where nuggets over a few pennyweight are just not found, ever. So digging only high tones is safe and eliminates many large iron targets.

When in doubt, dig it out!

Steve Herschbach

 

[Digger Bob]

Yes to what Steve said. He beat me to it. One thing to add though; There are some nuggets of the pourus variety that do not give any signal whatsoever. I learned that the hard way when field testing the machine in Mariposa county. They screamed on a Goldmaster yet did not produce any sound at all with the TDI no matter what the settings. This was with the stock round loop. Since the Jimmy loop came out I can get a small signal from them at shallow depth. These aren't tiny nuggets either, 1 - 2 dwt.

Digger Bob

 

[fredm]

Bob; I realize this is a tardy response...
I thought Reg's input on the GS5abc/TDI had eliminated that problem with the "invisible" nuggets??? I know his detector could see those nuggets, but that may have been a modified goldquest...I am sure you know and that is good info to have for areas with porous type gold...

Fred

 

[Reg]

Hi Fred,

This is another tardy response about the GS 5 or the TDI and invisible gold. There is an internal adjustment that can help on many of the early models of the TDI and on the GS 5 that will help one be able to detect more of those invisible nuggets.

Now, Digger Bob, if you have influence at Whites or have someone at one of the service centers with knowledge of the TDI and you have one of the original 200 units, you can have the tech reduce the internal delay control to minimum. This will reduce the delay capability to about 7 to 8 usec. This will allow you to do much better on those pesky nuggets that are impossible to detect with a PI. It is amazing just how a couple of usec can make such a difference in detecting this type of gold.

There is a down side to this and that is, some of the FET's used may not allow the detector to work at the shorter delay. So, it may be a hit or miss. I didn't have any problem with mine, but I have heard there may be problems.

On a different note, I can understand why Whites doesn't set up the detectors this way to begin with. There are enough questions now without any new strange things happening and there can be some strange things happen at the 8 usec setting. The detector can be more sensitive to ground signals and a few more hotrocks also. Large coils may not work at the shorter settings either.

Reg